[Technical Field]
The present disclosure relates to a gas sensor element which detects a concentration of a specific gas in a measured gas and a gas sensor unit which are configured to include the gas sensor element.
[Background Art]
A gas sensor element which is configured to include a solid electrolyte body and an electrode provided on the solid electrolyte body and electrically detects a concentration of a specific gas in a measured gas by ionizing the measured gas has been known. In order to make such a gas sensor element usable as soon as possible, the solid electrolyte body and the electrode are required to be in an activated state early.
The activated state includes, for example, a state where the solid electrolyte body and the electrode are at appropriate temperatures for reaction of the specific gas and a state where a surface of the electrode is in an appropriate state for reaction of the specific gas. In particular, in order to achieve a surface in the appropriate state, Patent Literature 1 discloses a gas concentration detection device which includes a sensor electrode and a pump electrode as electrodes. A specific gas to be measured is ionized in the sensor electrode, and a concentration of the specific gas is detected based on an electric current (sensor current) corresponding to an amount of ionized specific gas. The gas concentration detection device is configured such that when a gas sensor element is activated, a removing voltage for removing oxygen is applied to the pump electrode so that a reducing gas is generated, and oxygen adsorbed to the sensor electrode reacts with the reducing gas and is removed. This allows the sensor electrode to be in a state where noise superimposed on a sensor current caused by an oxygen ion is reduced.